The electrophotographic photosensitive member is commonly used in an electrophotographic image forming process having a charging step, an exposure step, a developing step, a transfer step and a cleaning step. Of the electrophotographic image forming process, the cleaning step, in which a toner remaining on the electrophotographic photosensitive member after the transfer step, what is called transfer residual toner, is removed to clean the surface of the electrophotographic photosensitive member, is an important step in order to obtain sharp images. A cleaning method making use of a cleaning blade is a cleaning method operated by bringing the cleaning blade and the electrophotographic photosensitive member into friction with each other. Also, in recent years, in the charging step, a method has come prevalent in which the electrophotographic photosensitive member is directly charged by means of a charging roller. Thus, a phenomenon called “rubbing memory” may be given as one of important problems in such make-up that the charging roller and the cleaning blade come into contact or touch with the electrophotographic photosensitive member. This phenomenon is one of memory phenomena which is caused when the charging roller or cleaning blade kept in contact or touch with the electrophotographic photosensitive member and the electrophotographic photosensitive member have undergone any impact due to the vibration or fall that may come during physical distribution and they come rubbed together to generate positive electric charges on the surface of the electrophotographic photosensitive member.
A surface layer of the electrophotographic photosensitive member is commonly often formed by dip coating. The surface of such a surface layer formed by dip coating, i.e., the surface of the electrophotographic photosensitive member has a tendency to be smooth. Hence, this makes the area of contact (or touch) larger between the cleaning blade or charging roller and the surface of the electrophotographic photosensitive member to make frictional resistance larger between the cleaning blade or charging roller and the surface of the electrophotographic photosensitive member, so that there tends to be seen the above problem seriously.
In addition, in recent years, in order to improve image quality, toner particles are being made smaller in diameter. The smaller in diameter the toner particles are being made, the larger the area of contact is between the toner and the electrophotographic photosensitive member. This makes the toner adhere to the surface of the electrophotographic photosensitive member at a large force per unit mass, and hence the surface of the electrophotographic photosensitive member may come low cleanable. Accordingly, it is necessary to set the cleaning blade at a high touch pressure so as to keep the toner from slipping through. Since, however, the surface of the electrophotographic photosensitive member is smooth as stated above, it comes into highly close touch with the cleaning blade. Thus, they stand in such a set-up that any faulty images due to the rubbing memory more tend to occur. In particular, where any vibration is applied to, e.g., a process cartridge, the friction is greatly produced between the cleaning blade and the electrophotographic photosensitive member, and hence this problem is serious.
As a way of overcoming the problems attendant on the friction between these cleaning blade and charging roller and the electrophotographic photosensitive member, a technique is available which is disclosed in Japanese Patent Laid-open Application No. H10-142813. This Japanese Patent Laid-open Application No. H10-142813 discloses a technique in which phenyl groups substituted with fluorine are introduced at terminals of binder molecules so as to lessen the friction with the cleaning blade. Japanese Patent Laid-open Application No. 2000-75517 also discloses a technique in which a charge transporting material with a specific structure and a polycarbonate with a specific structure are combined to keep any memory from occurring.
From the viewpoint of less friction between the electrophotographic photosensitive member and the charging roller or cleaning blade, it is considered to be one means to make the electrophotographic photosensitive member change in surface profile. For example, Japanese Patent Application Laid-open No. 2001-066814 discloses a technique in which a stamper (stamping die) having a well-shaped unevenness is used to process the surface of the electrophotographic photosensitive member by compression forming.
However, even where the electrophotographic photosensitive members disclosed in Japanese Patent Laid-open Applications No. H10-142813 and No. 2000-75517 are used, the memory caused by their friction with members coming into contact or touch with the electrophotographic photosensitive member may come about under severer conditions as in a vibration test, and it is sought to make further improvement.
Where the finely surface-processed electrophotographic photosensitive member disclosed in Japanese Patent Application Laid-open No. 2001-066814 is used and it is an electrophotographic photosensitive member with shallow wells in its uneven surface profile, it is unable to sufficiently reduce the area of contact (or touch) between the surface of the electrophotographic photosensitive member and the charging roller or cleaning blade that is an elastic member. Hence, the effect of keeping the rubbing memory from occurring can not well be obtained in some cases.